#!/usr/bin/env python3

# Copyright (c) 2018-2021 Markus Blöchl <ususdei@gmail.com>
#
# This file is part of qutebrowser.
#
# qutebrowser is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# qutebrowser is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with qutebrowser.  If not, see <https://www.gnu.org/licenses/>.

"""
# Introduction

This is a [qutebrowser][2] [userscript][5] to fill website credentials from a [KeepassXC][1] password database.


# Installation

First, you need to enable [KeepassXC-Browser][6] extensions in your KeepassXC config.


Second, you must make sure to have a working private-public-key-pair in your [GPG keyring][3].


Third, install the python module `pynacl`.


Finally, adapt your qutebrowser config.
You can e.g. add the following lines to your `~/.config/qutebrowser/config.py`
Remember to replace `ABC1234` with your actual GPG key.

```python
config.bind('<Alt-Shift-u>', 'spawn --userscript qute-keepassxc --key ABC1234', mode='insert')
config.bind('pw', 'spawn --userscript qute-keepassxc --key ABC1234', mode='normal')
```


# Usage

If you are on a webpage with a login form, simply activate one of the configured key-bindings.

The first time you run this script, KeepassXC will ask you for authentication like with any other browser extension.
Just provide a name of your choice and accept the request if nothing looks fishy.


# How it works

This script will talk to KeepassXC using the native [KeepassXC-Browser protocol][4].


This script needs to store the key used to associate with your KeepassXC instance somewhere.
Unlike most browser extensions which only use plain local storage, this one attempts to do so in a safe way
by storing the key in encrypted form using GPG.
Therefore you need to have a public-key-pair readily set up.

GPG might then ask for your private-key passwort whenever you query the database for login credentials.


[1]: https://keepassxc.org/
[2]: https://qutebrowser.org/
[3]: https://gnupg.org/
[4]: https://github.com/keepassxreboot/keepassxc-browser/blob/develop/keepassxc-protocol.md
[5]: https://github.com/qutebrowser/qutebrowser/blob/master/doc/userscripts.asciidoc
[6]: https://keepassxc.org/docs/KeePassXC_GettingStarted.html#_setup_browser_integration
"""

import sys
import os
import socket
import json
import base64
import subprocess
import argparse

import nacl.utils
import nacl.public


def parse_args():
    parser = argparse.ArgumentParser(description="Full passwords from KeepassXC")
    parser.add_argument('url', nargs='?', default=os.environ.get('QUTE_URL'))
    parser.add_argument('--socket', '-s', default='/run/user/{}/org.keepassxc.KeePassXC.BrowserServer'.format(os.getuid()),
                        help='Path to KeepassXC browser socket')
    parser.add_argument('--key', '-k', default='alice@example.com',
                        help='GPG key to encrypt KeepassXC auth key with')
    parser.add_argument('--insecure', action='store_true',
                        help="Do not encrypt auth key")
    return parser.parse_args()


class KeepassError(Exception):
    def __init__(self, code, desc):
        self.code = code
        self.description = desc

    def __str__(self):
        return f"KeepassXC Error [{self.code}]: {self.description}"


class KeepassXC:
    """ Wrapper around the KeepassXC socket API """
    def __init__(self, id=None, *, key, socket_path):
        self.sock        = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
        self.id          = id
        self.socket_path = socket_path
        self.client_key  = nacl.public.PrivateKey.generate()
        self.id_key      = nacl.public.PrivateKey.from_seed(key)
        self.cryptobox   = None

    def connect(self):
        if not os.path.exists(self.socket_path):
            raise KeepassError(-1, "KeepassXC Browser socket does not exists")
        self.client_id = base64.b64encode(nacl.utils.random(nacl.public.Box.NONCE_SIZE)).decode('utf-8')
        self.sock.connect(self.socket_path)

        self.send_raw_msg(dict(
            action    = 'change-public-keys',
            publicKey = base64.b64encode(self.client_key.public_key.encode()).decode('utf-8'),
            nonce     = base64.b64encode(nacl.utils.random(nacl.public.Box.NONCE_SIZE)).decode('utf-8'),
            clientID  = self.client_id
        ))

        resp = self.recv_raw_msg()
        assert resp['action'] == 'change-public-keys'
        assert resp['success'] == 'true'
        assert resp['nonce']
        self.cryptobox = nacl.public.Box(
            self.client_key,
            nacl.public.PublicKey(base64.b64decode(resp['publicKey']))
        )

    def get_databasehash(self):
        self.send_msg(dict(action='get-databasehash'))
        return self.recv_msg()['hash']

    def lock_database(self):
        self.send_msg(dict(action='lock-database'))
        try:
            self.recv_msg()
        except KeepassError as e:
            if e.code == 1:
                return True
            raise
        return False


    def test_associate(self):
        if not self.id:
            return False
        self.send_msg(dict(
            action = 'test-associate',
            id     = self.id,
            key    = base64.b64encode(self.id_key.public_key.encode()).decode('utf-8')
        ))
        return self.recv_msg()['success'] == 'true'

    def associate(self):
        self.send_msg(dict(
            action = 'associate',
            key    = base64.b64encode(self.client_key.public_key.encode()).decode('utf-8'),
            idKey  = base64.b64encode(self.id_key.public_key.encode()).decode('utf-8')
        ))
        resp = self.recv_msg()
        self.id = resp['id']

    def get_logins(self, url):
        self.send_msg(dict(
            action = 'get-logins',
            url    = url,
            keys   = [{ 'id': self.id, 'key': base64.b64encode(self.id_key.public_key.encode()).decode('utf-8') }]
        ))
        return self.recv_msg()['entries']

    def send_raw_msg(self, msg):
        self.sock.send( json.dumps(msg).encode('utf-8') )

    def recv_raw_msg(self):
        return json.loads( self.sock.recv(4096).decode('utf-8') )

    def send_msg(self, msg, **extra):
        nonce = nacl.utils.random(nacl.public.Box.NONCE_SIZE)
        self.send_raw_msg(dict(
            action   = msg['action'],
            message  = base64.b64encode(self.cryptobox.encrypt(json.dumps(msg).encode('utf-8'), nonce).ciphertext).decode('utf-8'),
            nonce    = base64.b64encode(nonce).decode('utf-8'),
            clientID = self.client_id,
            **extra
        ))

    def recv_msg(self):
        resp = self.recv_raw_msg()
        if 'error' in resp:
            raise KeepassError(resp['errorCode'], resp['error'])
        assert resp['action']
        return json.loads(self.cryptobox.decrypt(base64.b64decode(resp['message']), base64.b64decode(resp['nonce'])).decode('utf-8'))



class SecretKeyStore:
    def __init__(self, gpgkey):
        self.gpgkey = gpgkey
        if gpgkey is None:
            self.path = os.path.join(os.environ['QUTE_DATA_DIR'], 'keepassxc.key')
        else:
            self.path = os.path.join(os.environ['QUTE_DATA_DIR'], 'keepassxc.key.gpg')

    def load(self):
        "Load existing association key from file"
        if self.gpgkey is None:
            jsondata = open(self.path, 'r').read()
        else:
            jsondata = subprocess.check_output(['gpg', '--decrypt', self.path]).decode('utf-8')
        data = json.loads(jsondata)
        self.id = data['id']
        self.key = base64.b64decode(data['key'])

    def create(self):
        "Create new association key"
        self.key = nacl.utils.random(32)
        self.id = None

    def store(self, id):
        "Store newly created association key in file"
        self.id = id
        jsondata = json.dumps({'id':self.id, 'key':base64.b64encode(self.key).decode('utf-8')})
        if self.gpgkey is None:
            open(self.path, "w").write(jsondata)
        else:
            subprocess.run(['gpg', '--encrypt', '-o', self.path, '-r', self.gpgkey], input=jsondata.encode('utf-8'), check=True)


def qute(cmd):
    with open(os.environ['QUTE_FIFO'], 'w') as fifo:
        fifo.write(cmd)
        fifo.write('\n')
        fifo.flush()

def error(msg):
    print(msg, file=sys.stderr)
    qute('message-error "{}"'.format(msg))


def connect_to_keepassxc(args):
    assert args.key or args.insecure, "Missing GPG key to use for auth key encryption"
    keystore = SecretKeyStore(args.key)
    if os.path.isfile(keystore.path):
        keystore.load()
        kp = KeepassXC(keystore.id, key=keystore.key, socket_path=args.socket)
        kp.connect()
        if not kp.test_associate():
            error('No KeepassXC association')
            return None
    else:
        keystore.create()
        kp = KeepassXC(key=keystore.key, socket_path=args.socket)
        kp.connect()
        kp.associate()
        if not kp.test_associate():
            error('No KeepassXC association')
            return None
        keystore.store(kp.id)
    return kp


def make_js_code(username, password):
    return ' '.join("""
        function isVisible(elem) {
            var style = elem.ownerDocument.defaultView.getComputedStyle(elem, null);

            if (style.getPropertyValue("visibility") !== "visible" ||
                style.getPropertyValue("display") === "none" ||
                style.getPropertyValue("opacity") === "0") {
                return false;
            }

            return elem.offsetWidth > 0 && elem.offsetHeight > 0;
        };

        function hasPasswordField(form) {
            var inputs = form.getElementsByTagName("input");
            for (var j = 0; j < inputs.length; j++) {
                var input = inputs[j];
                if (input.type === "password") {
                    return true;
                }
            }
            return false;
        };

        function loadData2Form (form) {
            var inputs = form.getElementsByTagName("input");
            for (var j = 0; j < inputs.length; j++) {
                var input = inputs[j];
                if (isVisible(input) && (input.type === "text" || input.type === "email")) {
                    input.focus();
                    input.value = %s;
                    input.dispatchEvent(new Event('input', { 'bubbles': true }));
                    input.dispatchEvent(new Event('change', { 'bubbles': true }));
                    input.blur();
                }
                if (input.type === "password") {
                    input.focus();
                    input.value = %s;
                    input.dispatchEvent(new Event('input', { 'bubbles': true }));
                    input.dispatchEvent(new Event('change', { 'bubbles': true }));
                    input.blur();
                }
            }
        };

        function fillFirstForm() {
            var forms = document.getElementsByTagName("form");
            for (i = 0; i < forms.length; i++) {
                if (hasPasswordField(forms[i])) {
                    loadData2Form(forms[i]);
                    return;
                }
            }
            alert("No Credentials Form found");
        };

        fillFirstForm()
    """.splitlines()) % (json.dumps(username), json.dumps(password))


def main():
    if 'QUTE_FIFO' not in os.environ:
        print(f"No QUTE_FIFO found - {sys.argv[0]} must be run as a qutebrowser userscript")
        sys.exit(-1)

    try:
        args = parse_args()
        assert args.url, "Missing URL"
        kp = connect_to_keepassxc(args)
        if not kp:
            error('Could not connect to KeepassXC')
            return
        creds = kp.get_logins(args.url)
        if not creds:
            error('No credentials found')
            return
        # TODO: handle multiple matches
        name, pw = creds[0]['login'], creds[0]['password']
        if name and pw:
            qute('jseval -q ' + make_js_code(name, pw))
    except Exception as e:
        error(str(e))


if __name__ == '__main__':
    main()

